More and more people believe that extraterrestrial life does exist elsewhere in the universe. But what if this extraterrestrial life invades Earth?

Would they want to harvest the human race or possibly destroy us? Would the human race even stand a chance?

We've read the books, we've seen the movies. War of the Worlds, V, Independence Day.
But they're all fiction, right? Well, probably not. New science is
suggesting that aliens may be very real, and that they may not be as
cuddly as E.T.

Host Michelle Rodriguez brings together top scientists, military strategists and writers to dramatize what would happen if and when aliens attacked.

The most well-known alien invasion scenarios involve the aliens landing on Earth, destroying or abducting people, fighting and defeating Earth's military forces, and then destroying Earth's major cities.

Usually, the bulk of the story follows the battles between the invaders and Earth's armies, as in The War of the Worlds.

However, not all alien invasion stories follow this plot. In some accounts, the alien invaders will covertly subvert human society using disguises, shapechanging, creating conflict in humanity and let humans destroy themselves, or human allies.

In other depictions, the aliens score an overwhelming victory over humanity and the bulk of the story occurs after the aliens have taken over.

Sometimes, the aliens do not come from space, but from another dimension. And in some fiction, the invaders may not actually be aliens, but demonic creatures.

The alien invasion is a common theme in science fiction stories and film, in which extraterrestrial life invades Earth to either exterminate and supplant human life, enslave it under a colonial system, harvest humans for food, or destroy the planet altogether.

The invasion scenario has been used as an allegory for a protest against military hegemony and the societal ills of the time. H.G. Wells' novel The War of the Worlds is often viewed as an indictment of European colonialism and its "gunboat diplomacy"—setting a common theme for some politically motivated future alien invasion stories.

The theme also exploits invasion panics that were common when science fiction was first emerging as a genre.Prospects of invasion tended to vary with the state of current affairs, and current perceptions of threat. Alien invasion was a common metaphor in US science fiction during the Cold War, illustrating the fears of foreign (e.g. Soviet Union) occupation and nuclear devastation of the American people.

Examples of these stories include "The Liberation of Earth" by William Tenn and The Body Snatchers. In the invasion trope, fictional aliens contacting Earth tend to either observe (sometimes using experiments) or invade, rather than help the population of Earth acquire the capacity to participate in interplanetary affairs.

There have been a few exceptions, such as the alien-initiated first contact that begins the 1951 film The Day the Earth Stood Still, and the Vulcan-initiated first contact that concludes the 1996 film Star Trek: First Contact (although after a failed invasion by the Borg in the rest of the film).

In both cases, aliens decide to visit Earth only after noticing that its inhabitants have reached a threshold level of technology: nuclear weapons combined with space travel in the first case, and faster-than-light travel using warp drive technology in the second. Technically a human invasion of an alien species is also an alien invasion, as from the point of view of the aliens, humans are also aliens.